Numerous references disclose diltiazem in sustained release formulations which utilize microencapsulation technology. For example are the following:
U.S. Pat. No. 4,452,042, issued to Samejima et al. on Sept. 17, 1985;
U.S. Pat. No. 4,462,982, issued to Samejima et al. on July 31, 1984;
U.S. Pat. No. 4,443,497, issued to Samejima et al. on Apr. 17, 1984; and
U.S. Pat. No. 4,411,933, issued to Samejima et al. on Oct. 25, 1983.
Similarly, numerous publications have disclosed devices which rely upon an osmotically regulated membrane for the controlled delivery of pharmaceuticals, such as diltiazem. For example, are the following:
Belgian Application No. 900817, published on Feb. 1, 1985 discloses a device comprising a semipermeable wall, an osmopolymer, such as poly(ethyleneoxide) and an active ingredient.
Belgian Application No. 900,824 also published on Feb. 1, 1985 discloses a core and a membrane having variable permeability.
Belgian Application No. 898,819, published on May 30, 1984, discloses a device for controlled drug delivery containing two compositions, including poly(ethyleneoxide).
Belgian Application No. 903,540 published Feb. 17, 1986 discloses a sustained release powder, which can be formulated into an ointment, suspension etc.
Belgian Application No. 901,359 published Apr. 16, 1985 discloses a controlled release diltiazem formulation containing granules and a semipermeable external membrane.
Japanese Application No. 175,144 published on Apr. 13, 1984, discloses a sustained release thermoset or thermoplastic resin.
Japanese Application No. 170,440 published on Apr. 5, 1984, discloses a sustained release tablet which utilizes hardened oil.
Japanese Kokai No. 62/5915, published Jan. 12, 1987, discloses diltiazem in combination with an acrylic acid resin.
Japanese Kokai No. 61/212517, published Sept. 20, 1986 discloses the use of diltiazem in combination with hydrogenated oils.
Japanese Kokai No. 59/10512 published Jan. 20, 1984, discloses microencapsulation of diltiazem, which is coated with ethylcellulose.
Panoz and Geohagan, U.S. Pat. No. 4,721,619 disclose an alternating arrangement (between 50 and 200 layers) of diltiazem, organic acid and lubricant layers and polymeric material layers built upon a central inert core.
Schor et al., U.S. Pat. No. 4,389,393 discloses a sustained release tablet which is one or more hydroxypropylmethyl celluloses of a mixture of one or more hydroxypropylmethyl celluloses and up to 30% by weight of the mixture of methylcellulose, sodium carboxymethyl cellulose and/or other cellulose ether, and wherein at least one of the hydroxypropylmethyl celluloses has a methoxy content of 16-24 weight percent, a hydroxypropyl content of 4-32 weight percent and a number average molecular weight of at least 50,000 and wherein the carrier base material constitutes less than about one third of the weight of the solid unit dosage form. Schor et al. do not include calcium channel blockers and in particular diltiazem as possible active ingredients (see column 4, lines 29 to 65).
However, none of the references disclose a diltiazem tablet formulation utilizing a uniformly dispersed hydrophilic matrix which gives an immediate release preparation.